There is compelling evidence to suggest that there is a strong correlation between the sharply increasing levels of atmospheric CO2 with a commensurate increase in global surface temperatures. This effect is commonly known as Global Warming. Of the various sources of the CO2 emissions, there are a vast number of small, widely distributed emitters that are impractical to mitigate at the source. Additionally, large scale emitters such as hydrocarbon-fueled power plants are not fully protected from exhausting CO2 into the atmosphere. Combined, these major sources, as well as others, have lead to the creation of a sharply increasing rate of atmospheric CO2 concentration. Until all emitters are corrected at their source, other technologies are required to capture the increasing, albeit relatively low, background levels of atmospheric CO2. Efforts are underway to augment existing emissions reducing technologies as well as the development of new and novel techniques for the direct capture of ambient CO2. These efforts require methodologies to manage the resulting concentrated waste streams of CO2 in such a manner as to prevent its reintroduction to the atmosphere.
The production of CO2 occurs in a variety of industrial applications such as the generation of electricity power plants from coal and in the use of hydrocarbons that are typically the main components of fuels that are combusted in combustion devices, such as engines. Exhaust gas discharged from such combustion devices contains CO2 gas, which at present is simply released to the atmosphere. However, as greenhouse gas concerns mount, CO2 emissions from all sources will have to be curtailed. For mobile sources the best option is likely to be the collection of CO2 directly from the air rather than from the mobile combustion device in a car or an airplane. The advantage of removing CO2 from air is that it eliminates the need for storing CO2 on the mobile device.
Extracting carbon dioxide (CO2) from ambient air would make it possible to use carbon-based fuels and deal with the associated greenhouse gas emissions after the fact. Since CO2 is neither poisonous nor harmful in parts per million quantities, but creates environmental problems simply by accumulating in the atmosphere, it is possible to remove CO2 from air in order to compensate for equally sized emissions elsewhere and at different times.
Most prior art methods, however, result in the inefficient capture of CO2 from air because these processes heat or cool the air, or change the pressure of the air by substantial amounts. As a result, the net loss in CO2 is negligible as the cleaning process may introduce CO2 into the atmosphere as a byproduct of the generation of electricity used to power the process.
Various methods and apparatus have been developed for removing CO2 from air. For example, we have recently disclosed methods for efficiently extracting carbon dioxide (CO2) from ambient air using capture solvents that either physically or chemically bind and remove CO2 from the air. A class of practical CO2 capture sorbents include strongly alkaline hydroxide solutions such as, for example, sodium or potassium hydroxide, or a carbonate solution such as, for example, sodium or potassium carbonate brine. See for example published PCT Application PCT/US05/29979 and PCT/US06/029238.
There are also many uses for sequestered CO2. This includes the use of CO2 in greenhouses where higher levels of CO2 contribute to increased plant growth. CO2 may also be supplied to algae cultures. Researchers have shown that algae can remove up to 90% of gaseous CO2 from air streams enriched in CO2 and can also reduce the CO2 concentration in ambient air.